1. Field of Invention
The present invention relates to photosensitive compounds that generate free radicals upon exposure to light. More particularly, it relates to derivatives of halomethyl-1,3,5-triazines.
2. Discussion of the Prior Art
Compounds that decompose to generate free radicals (free radical generating agents) upon exposure to light are well known in the graphic arts. Organic halogen compounds, which are capable of generating free radicals such as a chlorine free radical or a bromine free radical upon exposure to light, have been widely used as photoinitiators in photopolymerizable compositions, as photoactivators in free radical photographic compositions, and as photoinitiators for reactions catalyzed by acids formed by light. The spectral sensitivity of these compositions may be broadened by the addition of sensitizers which, in essence, transfer their absorbed energy to the organic halogen compound. The use of such halogen compounds in photopolymerization processes and free radical photographic processes have been described in Kosar, Light-Sensitive Systems, J. Wiley & Sons (New York, 1965) pp. 180-181, 361-370.
Halomethyl-1,3,5-triazines are known to be initiators for a number of photochemical reactions. They are employed to produce free radicals for initiating polymerization or color changes and for initiating secondary reactions upon liberation of acid by the interaction of the free-radicals when hydrogen donors are present.
Examples of the use of halomethyl-1,3,5-triazines in the free radical polymerization of acrylate monomers are described in U S. Pat. No. 3,905,815; U.S. Pat. No. 3,617,288; U.S. Pat. No. 4,181,752; U.S. Pat. No. 4,391,687; U.S. Pat. No. 4,476,215; and DE 3,517,440. U.S. Pat. No. 3,779,778 discloses the photoinitiated acid catalyzed decomposition of pyranyl ether derivatives to produce photosolubilizable compositions useful as positive printing plates. Chromophore substituted styryl-1,3,5-triazines and their uses are disclosed in U.S. Pat. No. 3,987,037 and U.S. Pat. No. 3,954,475. Radiation sensitive compositions containing bi- and polyaromatic substituted triazines are disclosed in U.S. Pat. No. 4,189,323.
In compositions, the sensitivity of halomethyl-1,3,5-triazines to actinic radiation of a particular range of wavelengths can be increased by the incorporation of known ultraviolet and visible light sensitizers including cyanine, carbocyanine, merocyanine, styryl, acridine, polycyclic aromatic hydrocarbons, polyarylamines and amino-substituted chalcones. Cyanine dyes are described in U.S. Pat. No. 3,495,987. Styryl dyes and polyarylamines are described in Kosar, Light Sensitive Systems, J. Wiley and Sons (New York, 1965), pages 361-369. Polycyclic aromatic hydrocarbons useful as sensitizers, an example of which is 2-ethyl-9,10-dimethoxyanthracene, are described in U.S. Pat. No. 3,640,718. Amino substituted chalcones useful as sensitizers are described in U.S. Pat. No. 3,617,288. Halomethyl-1,3,5-triazines are used in conjunction with dialkylamino aromatic carbonyl compounds disclosed in U.S. Pat. No. 4,259,432; 2-(benzoylmethylene)-5-benzothiazolidene thiazole -4-1 compounds disclosed in E application 0109291, May 23, 1984; 3-keto-substituted coumarin compounds disclosed in U.S. Pat. No. 4,505,793; U.S. Pat. No. 4,239,850; Jpn. Kokai Tokkyo Koho JP 60 60,104 (85 60104); an Ger/ Offen 2,851,641.